The MEXICO project: The Database and Results of Data Processing and Interpretation Herman Snel, Gerard Schepers (ECN), Arn é Siccama (NRG). Introduction. MEXICO project = M odel EX periments I n Co ntrolled Conditions (European Union project, Framework Programme 5)
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The MEXICO project: The Database and Results of Data Processing and Interpretation Herman Snel, Gerard Schepers (ECN), Arné Siccama (NRG)
DU 91 W2 250
Risø A121
2.25 m
Kulite instrumented sections:
25% and 35 % DU 91 W2 250
60% Riso A121
82% and 92% NACA 64 418
NACA 64418

Zero rotor azimuth: blade 1 vertically upward Processing and Interpretation
Y
PIV planes at 270 degrees azimuth
PIV traverse tower with two cameras, aimed at horizontal PIV sheet of 35*42 cm2 in horizontal symmetry plane of the rotor
Seeding (tiny soap bubbles) injected in settling chamber.
Sheet is illuminated by laser flashes at 200 nanosecond interval and photographed.
Sheet is subdivided into ‘interrogation windows’ (79*93, 4.3*4.3mm2). Velocity vector is the vector giving maximum correlation between these two shots.
Flow field measurements, stereo PIVPhoto: Gerard Schepers
All data shown for tip speed of 100 m/s and 2.3° tip angle, zero yaw
Tunnel speeds of 10 m/s, 15 m/s and 24 m/s
l = 4.17
l = 6.7
Cylindrical vortex wake model
l = 10
The first intelligible pressure distribution appears in the quick look system, during the measurements
Flow direction
To blade tip
Attached flow l = 6.7:
Thin viscous wake, left by passing blade
Stalled flow l = 4.17:
Much thicker blade wake and ‘trailing vortex’ at location of large jump in bound vorticity, explains chaotic behaviour in velocity decay
Blade tip position at 2.25 m 82% span.
Axial velocity in radial traverse in rotor plane, for 0 and 120 azimuthShows good repeatability and coherence between different PIV sheets
Measured Inflow for blade just below and just above PIV sheet. PIV sheet always at 270 ° azimuth position
Blade tip position
az = 40°
az = 20 °
az = 40°
az = 20 °
Difference of approximately 5 m/s, 1/3 of free tunnel speed !
Trajectories for 3 tip speed ratios 82% span.
Tip vortex trajectories, axial flowl = 10
l =6.67
l = 4.17
l = 4.17
l = 6.67
l = 10
Vortex position against time: transportation speed constant!
V 82% span.wake
Y
tunnel axis
c
Vw
Rotor plane
Wake skew angle c
Vortex trajectories for 30 degrees yawFlow direction
Rotor plane position, seen from above
Vortex roll up inward of tip position
Blade tip position
Flow direction
tunnel 6.7, tip angle of 2.3° and zero yaw
model
Some grid details, tunnel environment included!blade
1/3 of the region covered, with symmetry boundary conditions
5.3 M cells, including tunnel environment
Calculated expansion much lower than measured !!??
Radial traverse at 30 cm behind rotor qualitatively good.
3D stall is observed in computations, most likely not present in tip area